Spatial distribution characteristics of soil organic carbon density in a tropical mountain rainforest of Jianfengling, Hainan Island, China

Forest soil organic carbon ( SOC) is the main component of the terrestrial carbon reservoir, and plays a crucial role in the Earth's carbon cycle. This study aimed to quantify the spatial heterogeneity and distribution patterns of SOC density. The study was conducted in a 60 hm2 forest plot in a tropical mountain rainforest of Jianfengling, Hainan Island, China, using field investigation, laboratory analysis, and geostatistical methods. The results showed that the mean SOC density at different soil profile depths (A [0-10 cm], B [10-30 cm], and C [30-60 cm]) was 2.699, 2.782, 2.434 kg/m2, respectively. The differences for A versus C and, B versus C layers were statistically significant (P < 0.05), but there was no significant difference between A and B layers ( P > 0.05) . Cross-validation results showed that the most fitted models for SOC density at different layers was exponential for A and spherical for B and C. The ranges of SOC density were 54.2 m, 70.9 m, and 97.2 m for A, B, and C, respectively, while